The long term objective of our research is to develop a high-strength particulate composite material composed of bone particles and gelatin that can be used to assist in fracture fixation. When mixed, the composite should be a viscous paste suitable for injection into travecular interstices. It should then harden to provide structural reinforcement to the injured region. The composite should act biologically as an allogenic bone graft and should eventually be resorbed and replaced by host bone. Althugh the principal intended application is fixation of osteoporotic fractures in elderly patients, such a composite material could have numerous other applications in orthopaedics including tumor surgery and fixation of prosthetic devices. The specific aims are to conduct a biomechanical optimization of the physical, chemical and structural variables controlling the mechanical behavior of the system. A bovine-based model composite system will be used to study the effects of bone particulate size distribution, the use of organic and inorganic cross-linking agents, and the addition of biodegradable reinforcing fibers and gel restraining salts. Human cadaver cancellous bone fracture models will be developed for testing the composite's effectiveness in fracture fixation. Optimized techniques for manufacture of bovine-based gelatin will be developed and adapted to use withr rabbit and sheep bone to minimize immunologic incompatibilities in in-vivo model systems. In-vivo fracture healing models through travecular bone will be developed in the rabbit and sheep for the study of fracture healing biology and biomechanics with the composite. Biomechanical testing, light microscopy, hostology and scanning electromicroscopic techniques will be used to study the augmentation of normal fracture healing. Gelatin manufacturing techniques will then be adapted for use with human bone and suitable sterilization techniques will be developed. Using cadaver model systems, optimized fixation methods for use with the bone/gelatin particulate composite will be tested. Structural failure tests will be performed using model fractures of the distal radius proximal femur and proximal tibia. With these background data, permission will be sought from the Institutional Review Board to use the human bone composite for fixation of certain fractures in selected human patients.